1. Field of the Invention
The present invention relates to a tightener, and more particularly to a strap tightener that has less wear between the pivot pin and the lever and the wing plates when releasing the strap.
2. Description of Related Art
With reference to FIGS. 5 and 6, a conventional strap tightener in accordance with the prior art comprises a base plate (50), a U-shaped seat (60), a lever (70) and a ratchet device. The U-shaped seat (60) is mounted on the base plate (50). The lever (70) is pivotally mounted on the seat (60) by a pivot pin (80). The ratchet device is mounted between the lever (70) and the seat (60).
The base plate (50) has a distal edge and a proximal edge parallel to each other. The distal edge of the base plate (50) is bent to form a hook (500). A slot (52) with two ends is defined in the base plate (50) near and parallel to the proximal edge through which a strap (100) can pass. A pair of ears (51) extends perpendicular from the base plate (50) in a direction opposite to the hook (500) near the distal edge of the base plate (50). The ends of the slot (52) correspond to the respective ears (51). Each of the ears (51) has a through hole (511) defined to align with the through hole (511) in the other ear (51). A bore (53) is defined in the base plate (50) between the pair of ears (51) and the slot (52).
The seat (60) includes two wing plates (600) parallel to each other. The wing plates (600) are oriented perpendicular to the proximal and distal edges of the base plate (50), have first ends near the distal edge of the base plate (50) and second ends near the proximal edge of the base plate (50). The wing plates (600) are connected by a bridge (601) to form a U-shape. A retaining plate (602) extends upward from one side of the bridge (601) near the pair of ears (51), and a hole (604) is defined in the retaining plate (602). A through hole (61) is defined in the first end of each wing plate (600) to correspond to the through holes (511) in the ears (51). A through hole (603) is defined in the bridge (601) and corresponds to the bore (53) in the base plate (50). After the through holes (61) in the wing plates (600) align with the through holes (511) in the ears (51), a bolt (not numbered) extends through the bore (53) in the base plate (50) and the through hole (603) in the bridge (601). A pivot hole (62) is defined in the second end of each of the wing plates (600), and a stop (63) extends from the second end of each of the wing plates (600). The stop (63) has a slot (631) defined near the middle portion of the stop (63). A guide slot (64) is defined in each of the wing plates (600) between the through hole (61) and the pivot hole (62). The guide slot (64) is aligned with a radius of the pivot hole (62) in the corresponding wing plate (50) and an extended diameter of the hole (604) in the retaining plate (602) that is perpendicular to both wing plates (600). A brake pawl (65) has two opposite sides respectively sliding in the guide slots (64) and a stub (651) extending through the hole (604) in the retaining plate (602). A spring (652) is mounted around the stub (651) of the brake pawl (65) between the brake pawl (65) and the retaining plate (602) to push the brake pawl (65) toward the pivot hole (62).
The lever (70) has a distal end and a proximal end and includes two side plates (71) perpendicular to and integrally formed with a connecting plate (72) at the distal end. A retaining plate (74) extends perpendicular from the connecting plate (72) and has a through hole (741) defined in the retaining plate (74). The internal width of the two side plates (71) is greater than the external width of the two wing plates (600) such that a gap is formed between the corresponding side plates (71) and wing plates (600). A pivot hole (not shown) is defined in a proximal end of the side plates (71) and corresponds to the pivot hole (62) in the seat (60). The diameter of the pivot hole in the lever (70) is the same as the diameter of the pivot hole (62) in the seat (60). A cam (73) extends from the proximal end of the side plate (71) to push the brake pawl (65). A guide slot (711) is defined in the side plate (71) aligned with the center of the pivot hole in the side plate (71) and an extended diameter of the through hole (741) in the retaining plate (74) perpendicular to the side plates (71).
Two ratchet wheels (81) are respectively mounted in the gaps between the two side plates (71) and the two wing plates (600). A pivot pin (80) extends through the pivot hole in the lever (70), the pivot hole (62) in the wing plate (600) and the two ratchet wheels (81) to attach the lever (70) and the two ratchet wheels (81) to the seat (60). The pivot pin (80) includes two half-round bars (801), and each of the ratchet wheels (81) has two half-round holes (not shown) defined to correspond to each other and allow the half-round bar (801) to extend through corresponding half-round holes. Consequently, the pivot pin (80) is rotated by the two ratchet wheels (81) when the lever (70) is pivoted. The ratchet wheel (81) includes multiple teeth each having a sliding side and a limiting side. The limiting side engages with the brake pawl (65) so that the ratchet wheel (81) rotates only in the direction from the brake pawl (65) to the lever (70). The pivot pin (80) includes two opposite ends. A locking hole (802) is defined in each end to receive a locking pin (82) that is secured on the pivot pin (80) to prevent the pivot pin (80) from detaching from the seat (60) and the lever (70).
To operate the strap tightener, the ratchet wheel (81) is stopped by the brake pawl (65) when the lever (70) is pivoted toward the hook (500). A drive pawl (75) has two opposite sides sliding in the guide slot (711) in the side plate (71) of the lever (70). A stub (751) extends through the through hole (741) in the retaining plate (74) on the lever (70) from the drive pawl (75). A spring (752) is mounted around the stub (751) and between the drive pawl (75) and the retaining plate (74) to push the drive pawl (75) to engage with the ratchet wheel (81). The ratchet wheel (81) is rotated to drive the pivot pin (80) to roll the strap (100) when the lever (70) is pivoted away from the hook (500).
To release the tension on the strap, the lever (70) is moved outward relative to the hook (500) and the drive pawl (75) is moved to abut the stop (63). Then the user must press the drive pawl (75) toward the distal end of the lever (70) and simultaneously move the lever (70) until the end of the drive pawl (75) is received in the slot (631) in the stop (63). At the same time, the cam (73) in the lever (70) presses the brake pawl (65) away from the ratchet wheel (81) to release the ratchet wheel (81). With neither the brake pawl (65) nor the drive pawl (75) engaging the ratchet wheel (81), the user can pull the strap (100) through the strap tenser.
With reference to FIG. 6, the spring (652) pushes the brake pawl (65), and the brake pawl (65) actuates the cam (73) on the lever (70). The spring (752) pushes the drive pawl (75) and the drive pawl (75) actuates the stop (63) on the seat (60). Consequently, a shearing force formed by the lever (70) and the seat (60) due to the restitution force of the springs (652, 752) actuates the pivot pin (80) so that the friction between the seat (60) and the lever (70) and the pivot pin (80) is raised. The increased friction may shorten the useful life of the strap tightener.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional strap tightener.
The main objective of the present invention is to provide an improved strap tightener. A limit nub extends outward from each of the wing plates of the seat. An indent is defined in each of the cams of the side plates to correspond to the limit nub and receive the limit nub when releasing the strap to fix the position of the lever with respect to the seat. Consequently, the pivot holes in the seat and the lever have a good concentricity to reduce the shearing force between the lever, the seat and the pivot pin.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.